There are many plain paper electrophotographic copiers commercially available at the present time and in addition the body of patented prior art which has evolved for the past decades since the original invention of Carlson is quite extensive. Basically all copiers of this type operate on the same principles.
The original document or graphic article is illuminated and the light image thereof projected onto a previously charged electrophotographic drum, belt or planar member to acquire a latent image of the subject matter carried by the document on the surface of the electrophotographic member. The electrophotographic member is developed by applying toner particles thereto, either in a liquid suspension or in dry powder form, these toner particles being electroscopic in nature and thereby being attracted to the incremental areas of the electrophotographic member which have not been discharged by the light of the projected image. The discharged areas of the electrophotographic member do not attract the particles.
The developed image is then transferred from the electrophotographic member to a plain paper sheet, the toner is fixed to the sheet by heat or pressure or both and the resulting copy of the original document is ejected from the apparatus.
The copier of the invention operates in the same manner as described, but the invention is concerned with structural features which render the copier of the invention highly compact, simple, economical, reliable, light weight and yet efficient.
The convenience copier, as it is known, has taken the form of large, heavy and expensive apparatus using considerable electrical energy for operation and utilizing for the most part an extremely complex operating system. It has been a long-desired goal of makers of convenience copiers to provide a plain paper copier that is compact and economical. The goal is not believed to have been achieved until the advent of this invention, at least to the extent that is accomplished by this invention.
One attempted scheme which has found its way into many commercial copiers has been to provide a carriage which moves the original document over the projection station requiring complex drive mechanisms along with additional motors besides those operating the other required mechanisms. Moving carriages require space to achieve the full stroke of the carriage that normally extends beyond the usual chassis of the apparatus. Different size paper requires different size cassettes which may even protrude from the chassis.
Considering the procedure which must be followed in a convenience plain paper copier, unless the paper follows a serpentine path to the electrophotographic drum or belt or other electrophotographic member, the mechanisms must be laid out end to end resulting in the minimum length being dictated by the mechanisms plus the length of the paper. The serpentine path type of copier is complex because the paper is required to be stripped off a magazine where sheets are stacked, brought to the transfer station by way of rollers, belt and guides while making turns, transferred, fixed and ejected. Jams are often and difficult to clear. Even servicing the usual copier is difficult because the desire to make the apparatus compact decreases the accessibility of the different parts of the interior of the apparatus.
Convenience copiers must be constructed with certain requirements to render them efficient and reliable. The basic ones of these requirements are concerned with the consumables of the apparatus. There is toner to be replaced, there is an electrophotographic member which becomes worn and/or fatigued which is to be replaced, there are belts or sprocket chains to be inspected and/or replaced, there is a supply of paper to be replenished, there is a projection system to be adjusted or focussed (usually in the finished apparatus before shipping), there may be illuminating means to be varied and there is always the requirement that a serviceman should be able to have ready and facile access to the mechanism and electrical system for servicing.
These requirements tend to make the copier complex. In addition copiers are made with mechanisms and electrical systems for making multiple copies, for enlarging or reducing the size of the copy relative to the original document, for making light or dark copies, for enabling books to be copied, etc.
The invention in its basic and preferred form contemplates a simple, compact copier which makes a single copy at a time from a sheet type original document that is manually fed to the device. For multiple copies, the original is re-fed into the apparatus, being available when the copy cycle is complete because it passes through the illuminating and projecting station immediately. No enlargement or reduction is provided for. All of the remainder of the requirements which are stated above are provided in a manner to render the copier compact and efficient. Although not limited thereto, the invention enables a convenience copier to be constructed which is about the size of a small typewriter and of comparable if not lesser weight.